The purpose of the invention is to provide a chuck device with which rotation in the loosening direction of a rotating tube during tool exchange is facilitated, and the service life of ratchet teeth is prolonged by inhibiting wear thereof. Provided is a chuck device that opens and closes multiple claws 3, which are inserted in a hole 2a provided on the tip of a main body 2, by rotating a rotating tube 1 and that grips a tool 4 with said claws 3, wherein: a ring-shaped rotating body 8, which screwably engages with the claws 3 and rotates together with the rotating tube 1, is fitted on the main body 2 on the inside of the rotating tube 1; a ratchet teeth 5 ring is provided on the main body 2 or the rotating body 8; a detachable locking spring 9 that engages with the ratchet teeth 5 is provided; and an unlocking mechanism is provided so that when the rotating force in the tightening direction is reduced to zero after the gripping force on the tool 4 has reached a specified value due to rotation of the rotating tube 1 in the tightening direction, the unlocking mechanism forcibly releases the engagement of the ratchet teeth 5 with the locking spring 9.